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1.
Win-Bin Cheng 《Marine Geophysical Researches》2004,25(1-2):79-93
A joint analysis of gravity anomaly and seismic travel-time data has been used to construct a three-dimensional velocity structure for the northeastern extension of the northern South China Sea’s high-magnetic belt in the Taiwan region. The earthquake data used in this study was collected by the Central Weather Bureau Seismological Network from 1991 to 2002, while the gravity data around Taiwan was compiled by Hsu et al. (1998), Terr. Atmos. Oceanic. Sci., 9, 509–532, and Wang et al. (2002), >Terr. Atmos. Oceanic. Sc., 13, 339–354. A modified velocity model obtained by local earthquake tomography was used to construct an initial three-dimensional gravity model, using a linear velocity–density relationship. To derive a crustal velocity–density model that accounts for both types of observations, this study performed a sequential inversion of travel-time and gravity data. The main features of our three-dimensional velocity model are:(1) an uplifted zone with velocity greater than 6.5 km/s being observed in the lower crust, (2) the width and the shape of the uplifted zone being found to be strongly correlated with the high-magnetic belt, (3) a trend by which the lower crustal high-velocity zone turns from northeast to north in central Taiwan, where the high-magnetic zone was truncated. A combination of seismic, gravity, and structural interpretations suggests that the crustal deformation relating to the magnetic truncation observed in northwestern Taiwan could be correlated closely with the collision between the Philippine Sea plate and the Asian continental margin. 相似文献
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The application of advanced enhancement techniques for geophysical anomalies to global gravity (WGM2012) and magnetic (EMAG2) models sheds light on the complex tectonic evolution of the Rio Grande Rise (RGR) in the southern South Atlantic. Long wavelength Bouguer gravity lows indicate a thicker crust beneath of the ridge, whose nature can be related to a microcontinent or an excess of volcanism within the oceanic realm. Recently dredged continental rocks reinforce the hypothesis of a microcontinent or, at least, slivers of continental crust. However, the reserval magnetic pattern of the processed magnetic anomalies provide no evidence of aborted spreading center similar to the well-studied Jan Mayen microcontinent and the surrounding (inactive) Aegir and (active) Kolbeinsey ridges in the North Atlantic Ocean. The reversal magnetic anomalies show a series N-S trending parallel stripes roughly follow the current South American coastline and segmented by E-W oriented oceanic fracture zones (FZs). The magnetic stripes are bended eastwards at the RGR, showing a more complex magnetic pattern similar to that in the Iceland. The aborted Cruzeiro do Sul Rift (CSR) and the Jean Charcot Chain (JCC) are structures that cross the RGR and contribute to the understanding of the tectonic evolution of the South Atlantic Ocean. NW-SE oriented extensive gravity lows and bathymetric valleys, which mark the CSR, are segmented by E-W trending magnetic lineaments related to FZs. This structural configuration suggests that the extensional event, which formed the rift and the seamounts chain, was replaced by strike-slip movements along the FZs. In addition, we constructed a plate kinematic model for the evolution of the RGR based on bathymetric, free-air and Bouguer gravity and magnetic data. Our model comprises five main stages of the RGR formation and evolution between late Cretaceous and Paleocene (ca. 95 - 60 Ma), separated by published seafloor isochrones. The proposed model suggests that the RGR was built at the mid-Atlantic ridge by increased magmatism probably related to the Tristan da Cunha hotspot. 相似文献
3.
简述了SGG数据恢复局部重力场的理论本质以及卫星重力梯度边值问题;详细介绍了当前国内外利用SGG进行局部重力场求解的研究进展,并将已有的求解方法总结归纳为三类：模型法、计算法和组合法,同时对各种方法的概念和研究现状作了详细介绍;最后总结了SGG数据求解局部重力场的发展前景和思考建议。 相似文献
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This study describes an automatic berthing system with mooring lines. It is designed to be berthed by using mooring device on the upper deck of a ship. It is to berth once maintaining parallel with the quay by controlling both forward and aft breast lines. Berthing method is used through length adjustment of mooring lines connected between ship and quay by controlling the angular velocity and the torque of hydraulic motor in mooring device. The study is conducted under three changing conditions of draft, such as even-keel, rise of the gravity center and trim to stern. Variables affecting berthing stability are determined based on the control performance of each condition. Bond graphs method is used to model the system. Controller is designed as PID control method of reference-model algorithm. The control program is composed of synchronous control system based on the equations derived with the numerical analysis. The tank test is conducted to verify the usefulness of the control program. 相似文献
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ABSTRACTDifferent types of gravity observations are available over coastal areas. The main challenge for coastal geoid determination is the proper fusion of heterogeneous gravity data including land, shipborne, airborne, and altimetry-derived gravity data. This paper describes the gravity data fusion and the computation of the gravimetric quasigeoid in the coastal area of mainland China. An iterative procedure of the weighted least-squares prediction based on rectangular harmonic functions is used for merging the land, altimetric, shipborne, and airborne gravity data. Applying the analytical continuation method in Molodensky's theoretic frame, the merged gravity data are then used to determine the gravimetric quasigeoid model by using the generalized Stokes' integral in a remove-compute-restore fashion. The gravimetric quasigeoid model is compared with the height anomalies determined at 662 GPS leveling points over the coastal region of mainland China, where both the geodetic height and the normal height are known. The standard deviations of the differences in the coastal provinces range from 1.8 to 4.4 cm. For the entire computation area, the mean and standard deviation of the differences are 27.9 and 3.9 cm, respectively. 相似文献
8.
南沙海域中建南盆地的磁性基底及地壳结构 总被引：1，自引：0，他引：1
通过对南沙海域中建南盆地重磁资料的分析及反演计算,依据盆地的地质与地球物理特征,对地震资料难以解决的基底结构、性质进行了研究,确定了磁性基底与莫霍面深度,确定了地壳类型,并对盆地内的深部大断裂及磁性基岩属性作了推断,为今后的研究提供了依据。 相似文献
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根据最新调查获得的北黄海盆地海洋重力、海洋与航空磁力和多道地震资料,结合以往周边地区的资料,编制了北黄海空间重力异常图、布格重力异常图、磁力异常图。在重磁基础图件的基础上,通过解析延拓、任意方向导数计算、离散小波变换等处理,结合地震和地质资料,对北黄海北缘断裂带进行了综合分析。确定了北黄海北缘断裂带的存在,并对该断裂带的延伸长度、切割深度和性质进行了分析,指出北黄海北缘断裂带是辽东隆起与北黄海盆地的界线,断裂带两侧具有明显不同的地球物理场特征;而且断裂带具有多期活动的特点,对北黄海盆地的形成演化具有重要的控制作用。 相似文献
11.
在建立局部地区的地球重力场模型中,球冠谐分析是一种有效的方法。在球冠坐标系下建立重力场模型时,仅涉及到重力位的垂向分量,不必进行关于极角的微分运算,所以仅用单个正交基来建模,但若要在球冠坐标系下对重力场作进一步分析,如类似于平面处理的导数运算,来突出地质体的边界,要计算极角的微分,利用单个正交基表示则不易收敛,且误差较大。本文中作者采用两个正交基函数在球冠坐标系下对重力场建模,推导计算了径向导数和曲面导数模,并利用棱柱体正演模型进行检验,结果表明双基函数建模更适合曲面上的位场表示。最后计算了冲绳海槽地区卫星测高重力异常数据的曲面导数,径向导数清晰划分了东海陆架上大构造单元,曲面导数梯度带显示了东海陆架外缘隆起带,也指示了陆架盆地内的一些局部构造。这表明双基函数的球冠谐分析是一种有效的曲面位场建模方法。 相似文献
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从地球重力场测量要素出发,按照局部重力场模型、区域重力场模型、全球重力场模型求解的发展思路,分析了对地球重力场测量技术手段的要求。根据高-低卫星跟踪卫星的距离和距离变率开展定轨研究的概念,梳理了卫星跟踪卫星重力测量系统的发展。针对卫星跟踪卫星重力测量技术的内涵,分析了高-低卫星跟踪卫星测量模式（SST-hl）和高-低低卫星跟踪卫星测量模式（SST—hll）的地球重力场测量本质。 相似文献
13.
Yoshifumi Nogi Kumiko Nishi Nobukazu Seama Yoichi Fukuda 《Marine Geophysical Researches》2004,25(3-4):221-231
The seafloor spreading evolution in the Southern Indian Ocean is key to understanding the initial breakup of Gondwana. We
summarize the structural lineaments deduced from the GEOSAT 10 Hz sampled raw altimetry data as well as satellite derived
gravity anomaly map and the magnetic anomaly lineation trends from vector magnetic anomalies in the West Enderby Basin, the
Southern Indian Ocean. The gravity anomaly maps by both Sandwell and Smith 1997, J. Geophys. Res. 102, 10039–10054 and 10 Hz raw altimeter data show almost the same general trends. However, curved structural trends, which turn
from NNW–SSE in the south to NNE–SSW in the north, are detected only from gravity anomaly maps by 10 Hz raw altimeter data
just to the east of Gunnerus Ridge. NNE–SSW structural trends and magnetic anomaly lineation trends that are perpendicular
to them are observed between the Gunnerus Ridge and the Conrad Rise. To the west of Gunnerus Ridge, structural elements trend
NNE–SSW and magnetic polarity changes are normal to them. In contrast, almost NNW–SSE structural trends and ENE–WSW magnetic
polarity reversal strikes are dominant to the east of Gunnerus Ridge. Curved structural trends, which turn from WNW–ESE direction
in the south to NNE–SSW direction in the west, and magnetic polarity reversal strikes that are almost perpendicular to them
are observed just south of Conrad Rise. The magnetic polarity reversals may be parts of the Mesozoic magnetic anomaly sequence
that formed along side of the structural lineaments before the long Cretaceous normal polarity superchron. Curved structural
trends, detected only from gravity anomaly maps by 10 Hz raw altimeter data, most likely indicate slight changes in spreading
direction from an initial NNW–SSE direction to NNE–SSW. Our results also suggest that these curved structural trends are fracture
zones that formed during initial breakup of Gondwana. 相似文献
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Abstract The contribution of bathymetry to the estimation of gravity field related quantities is investigated in an extended test area in the Mediterranean Sea. The region is located southwest of the island of Crete, Greece, bounded between 33? ≤ ? ≤ 35? and 15? ≤ λ ≤ 25?. Gravity anomalies from the KMS99 gravity field and shipborne depth soundings are used with a priori statistical characteristics of depths in a least-squares collocation procedure to estimate a new bathymetry model. Two different global bathymetry models, namely JGP95E and Sandwell and Smith V8, are used to derive the depth a priori statistical information, while the estimated model is compared against both the global ones and the shipborne depth soundings to assess whether there is an improvement. Various marine geoid models are estimated using ERS1 and GEOSAT Geodetic Mission altimetry and shipborne gravity data. In that process, the effect of the bathymetry is computed using both the estimated and the original depths through a residual terrain modeling reduction. The TOPEX/Poseidon Sea Surface Heights, known for their high accuracy and precision, and the GEOMED solution for the geoid in the Mediterranean are used as control for the validation of the new geoid models and to assess the improvement that the estimated depths offer to geoid modeling. The results show that the newly estimated bathymetry agrees better (by about 30 to 300 m) with the shipborne depth soundings and provides smoother residual geoid heights and gravity anomalies (by about 8–20%) than those from global models. Finally, the achieved accuracy in geoid modeling ranges between 6 and 10 cm (1σ). 相似文献
16.
Compared to the northern South China Sea continental margin, the deep structures and tectonic evolution of the Palawan and Sulu Sea and ambient regions are not well understood so far. However, this part of the southern continental margin and adjacent areas embed critical information on the opening of the South China Sea (SCS). In this paper, we carry out geophysical investigations using regional magnetic, gravity and reflection seismic data. Analytical signal amplitudes (ASA) of magnetic anomalies are calculated to depict the boundaries of different tectonic units. Curie-point depths are estimated from magnetic anomalies using a windowed wavenumber-domain algorithm. Application of the Parker–Oldenburg algorithm to Bouguer gravity anomalies yields a 3D Moho topography. The Palawan Continental Block (PCB) is defined by quiet magnetic anomalies, low ASA, moderate depths to the top and bottom of the magnetic layer, and its northern boundary is further constrained by reflection seismic data and Moho interpretation. The PCB is found to be a favorable area for hydrocarbon exploration. However, the continent–ocean transition zone between the PCB and the SCS is characterized by hyper-extended continental crust intruded with magmatic bodies. The NW Sulu Sea is interpreted as a relict oceanic slice and the geometry and position of extinct trench of the Proto South China Sea (PSCS) is further constrained. With additional age constraints from inverted Moho and Curie-point depths, we confirm that the spreading of the SE Sulu Sea started in the Early Oligocene/Late Eocene due to the subduction of the PSCS, and terminated in the Middle Miocene by the obduction of the NW Sulu Sea onto the PCB. 相似文献
17.
KSS 31海洋重力仪配套接口子系统开发 总被引：1，自引：0，他引：1
介绍一种采用VC 语言开发成功的KSS 31型海洋重力仪导航系统适配的接口应用程序,对如何解决引进新型号设备与现有的系统(设备)集成(连接)问题有一定的借鉴作用。 相似文献
18.
基于106个月的Grace（gravity recovery and climate experiment）月重力场模型（120阶次）,消除了月重力场的月、季度及年度变化,得到了稳态的地球重力场模型（Grace_sta）。在2～120阶次之间,Grace_sta与已有高阶重力场EGM2008及EGM96三个模型的阶方差是一致的。在2～100阶次之间,Grace_sta模型误差阶方差要小于EGM2008与EGM96误差阶方差。在全球范围内,Grace_sta重力场的大地水准面与EGM2008相应阶次的大地水准面标准差约为3cm,与EGM96模型大地水准面差异则高达52cm。结果表明,Grace_sta足可以取代EGM2008重力场模型2～100阶次的低阶部分,新得到的稳态重力场模型可为海面地形分析提供了可靠的参考场。 相似文献
19.
东海陆架区中北部前第三系基底综合地球物理研究 总被引：6，自引：0，他引：6
从地震、钻井资料出发,结合周边地质特征,推断东海陆架区中北部存在中生界和古生界地层。结合地震资料,正演消除了海底和新生界密度不均匀在重力场上的影响,定量反演重、磁力异常并求取了重力基底和磁性基底。重力基底的特征在东西分带的大背景下表现出“靠陆侧南北分块,靠洋侧东西分带”的特点。西湖凹陷区的磁性基底与重力基底埋深大致相同,不一致地方可能是受岩体的影响。西湖凹陷以西地区,包括海礁凸起等单元,总体出现磁性基底埋深比重力基底埋深深2km左右,初步解释为古生界地层的反映。中生界地层厚度的分布也具有东西分带和南北分块特点。西湖凹陷西缘的中生界地层厚度大,其中带中生界虽然含有一定的火山岩或火山碎屑岩,但沉积岩更多,这对下一步的油气勘探有利。 相似文献
20.
《Marine Geodesy》2012,35(1):63-85
AbstractWe introduce an iterative inversion method to address the problems in high-order seafloor topography inversion using gravity data (gravity anomaly and vertical gravity gradient anomaly), such as the difficulty in computing the equation and the uniqueness of the calculation results. A part of the South China Sea is selected as the experimental area. Considering the coherence and admittance function of gravity topography and vertical gravity gradient topography, the inversion band of the gravity anomaly and vertical gravity gradient anomaly in the study area is 30?km–120?km. Seafloor topography models of different orders are constructed using an iterative method, and the performance of each seafloor topography model is analyzed against ETOPO1 and other seafloor topography models. The experimental results show that as the inversion order increases, the clarity and richness of seafloor topographic expression continuously improve. However, the accuracy of seafloor topography inversion does not improve significantly when the inversion order exceeds a certain value, which is related to the contribution of high-order seafloor topography to gravity information. The results show that the accuracy of BGT4 (inversion model constructed by the gravity anomaly) is slightly poorer than that of BVGGT4 (inversion model constructed by the vertical gravity gradient anomaly) in areas with complex topography, such as multi-seamounts and trenches, and the results are generally better in areas with flat seafloor topography. 相似文献